Recent advances in HER2-targeted therapy have made a dramatic impact on patient survival rates diagnosed with HER2-positive breast cancer. Selecting the appropriate treatment, however, requires simplified tests for HER2 overexpression, which is currently the bottleneck. Liquid biopsy offers a non-invasive and more sensitive method for diagnosing HER2-positive breast cancer. In this contract, we will explore the possibility that a novel capture technology, CAP-TECH, designed for the differential capture of exosomes (E-CAP) and oncosomes (O-CAP) enables rapid, reproducible isolation, and enrichment of exosomes and oncosomes from samples. We propose to: 1) optimize prototypes and develop rapid high-throughput-compatible isolation protocols capable of producing pure exosome and oncosome populations from human plasma, 2) confirm the integrity, purity, percent recovery of purified exosomes and oncosomes using physicochemical methods, and 3) perform a side-by-side comparison against current gold standards for exosome isolation and an initial clinical evaluation of HER2-positive oncosome isolation on confirmed HER2-positive patient samples. This work will lay the foundation for future product development and field-testing evaluations in Phase II. Success of this contract will provide a novel, high-throughput compatible, and cost-effective tool for the rapid differential isolation of exosomes and oncosomes from patient samples, which could greatly improve treatment selection, and patient outcomes.